She's alone. She's level 24. One of these things will matter more than the other. (Spoilers: it's her level.) She has a bevy of spells (even if most of them are buffs) and some decently-leveled Sword skills. Clustering up will result in spells to the face. (Spoilers: not her face.) Gang up on her and utilize chain attacks for the bonus; whomever gets the kill will get a nice pile of exp.